/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Spring.Expressions;

/// <summary>
/// Utility class that enables easy expression evaluation.
/// </summary>
/// <remarks>
/// <p>
/// This class allows users to get or set properties, execute methods, and evaluate
/// logical and arithmetic expressions.
/// </p>
/// <p>
/// Methods in this class parse expression on every invocation.
/// If you plan to reuse the same expression many times, you should prepare
/// the expression once using the static <see cref="Expression.Parse(string)"/> method,
/// and then call <see cref="IExpression.GetValue()"/> to evaluate it.
/// </p>
/// <p>
/// This can result in significant performance improvements as it avoids expression
/// parsing and node resolution every time it is called.
/// </p>
/// <p>
/// </p>
/// </remarks>
/// <author>Aleksandar Seovic</author>
public class ExpressionEvaluator
{
    /// <summary>
    /// Parses and evaluates specified expression.
    /// </summary>
    /// <param name="root">Root object.</param>
    /// <param name="expression">Expression to evaluate.</param>
    /// <returns>Value of the last node in the expression.</returns>
    public static object GetValue(object root, string expression)
    {
        IExpression exp = Expression.Parse(expression);
        return exp.GetValue(root, null);
    }

    /// <summary>
    /// Parses and evaluates specified expression.
    /// </summary>
    /// <param name="root">Root object.</param>
    /// <param name="expression">Expression to evaluate.</param>
    /// <param name="variables">Expression variables map.</param>
    /// <returns>Value of the last node in the expression.</returns>
    public static object GetValue(object root, string expression, IDictionary<string, object> variables)
    {
        IExpression exp = Expression.Parse(expression);
        return exp.GetValue(root, variables);
    }

    /// <summary>
    /// Parses and specified expression and sets the value of the
    /// last node to the value of the <c>newValue</c> parameter.
    /// </summary>
    /// <param name="root">Root object.</param>
    /// <param name="expression">Expression to evaluate.</param>
    /// <param name="newValue">Value to set last node to.</param>
    public static void SetValue(object root, string expression, object newValue)
    {
        IExpression exp = Expression.Parse(expression);
        exp.SetValue(root, null, newValue);
    }

    /// <summary>
    /// Parses and specified expression and sets the value of the
    /// last node to the value of the <c>newValue</c> parameter.
    /// </summary>
    /// <param name="root">Root object.</param>
    /// <param name="expression">Expression to evaluate.</param>
    /// <param name="variables">Expression variables map.</param>
    /// <param name="newValue">Value to set last node to.</param>
    public static void SetValue(object root, string expression, IDictionary<string, object> variables, object newValue)
    {
        IExpression exp = Expression.Parse(expression);
        exp.SetValue(root, variables, newValue);
    }
}
